Combined Impact of Climate Change, Cultivar Shift, and Sowing Date on Spring Wheat Phenology in Northern China

Distinct climate changes since the end of the 1980s have led to clear responses in crop phenology in many parts of the world. This study investigated the trends in the dates of spring wheat phenology in relation to mean temperature for different growth stages. It also analyzed the impacts of climate change, cultivar shift, and sowing date adjustments on phenological events/phases of spring wheat in northern China （NC）. The results showed that significant changes have occurred in spring wheat phenology in NC due to climate warming in the past 30 years. Specifically, the dates of anthesis and maturity of spring wheat advanced on average by 1.8 and 1.7 day （10 yr）-1. Moreover, while the vegetative growth period （VGP） shortened at most stations, the reproductive growth period （RGP） prolonged slightly at half of the investigated stations. As a result, the whole growth period （WGP） of spring wheat shortened at most stations. The findings from the Agricultural Production Systems Simulator （APSIM）-Wheat model simulated results for six representative stations further suggested that temperature rise generally shortened the spring wheat growth period in NC. Although the warming trend shortened the lengths of VGP, RGP, and WGP, the shift of new cultivars with high accumulated temperature requirements, to some extent, mitigated and adapted to the ongoing climate change. Furthermore, shifts in sowing date exerted significant impacts on the phenology of spring wheat. Generally, an advanced sowing date was able to lower the rise in mean temperature during the different growth stages （i.e., VGP, RGP, and WGP） of spring wheat. As a result, the lengths of the growth stages should be prolonged. Both measures （cultivar shift and sowing date adjustments） could be vital adaptation strategies of spring wheat to a warming climate, with potentially beneficial effects in terms of productivity.

Stability of patches of oasis landscape in arid areas:A case study of Sangong River Watershed,Xinjiang,China

绿洲的稳定性是在进化的过程和在干旱区域的绿洲的管理的关键科学问题之一。绿洲和它的表示的稳定性在不同规模也是不同的。这篇论文在 Tianshan 山的 Sangong 河分水岭与案例研究在风景补丁规模处理绿洲的稳定性。我们采用了 ther 激动地表达感情到进程 ther 的察觉到的、地理信息系统和数学统计方法激动地表达感情在 1978， 1987 和 1998 察觉到三个时期的图象，并且为在风景补丁规模代表绿洲稳定性提出途径。绿洲补丁的风景控制能力是动态风景变化的一种自然驱动力。在有它在它和另外的补丁之间的区域和形状复杂性和对比的风景变化增加以后的某个补丁类型的控制能力，和有它在它和另外的补丁之间的空间距离的还原剂。有最强壮的控制能力的补丁类型应该是风景的矩阵。绿洲风景补丁的变换源于自然、人为的驱动力，特别地人为的驱动力。变换比例越高，越多降低补丁类型的稳定性并且人为的骚乱越更强壮。有在在 1987 的 Sangong 河分水岭的最强壮的网控制能力的补丁类型是荒芜的草地，它是风景的矩阵；但是风景的矩阵在 1987 和 1998 被变成了灌溉陆地。绿洲风景进化上的风景补丁的控制能力逐渐地在程度也逐渐地减少了的 Sangong 河分水岭，和变化与时间减少了。这表明在风景补丁类型之中的相互作用通常通常趋于到还原剂，和绿洲风景补丁的自然稳定性趋于增加。然而，在风景补丁之中的变换由于集中的人的活动的增加更经常发生，它可能在绿洲风景引起环境资源补丁的更低的稳定性和介绍补丁的更高的稳定性。

Comparison of winter wheat yield sensitivity to climate variables under irrigated and rain-fed conditions

Crop simulation models provide alternative, less time-consuming, and cost-effective means of deter- mining the sensitivity of crop yield to climate change. In this study, two dynamic mechanistic models, CERES （Crop Environment Resource Synthesis） and APSIM （Agricultural Production Systems Simulator）, were used to simulate the yield of wheat （Triticum aestivum L.） under well irrigated （CFG） and rain-fed （YY） conditions in relation to different climate variables in the North China Plain （NCP）. The study tested winter wheat yield sensitivity to different levels of temperature, radiation, precipitation, and atmospheric carbon dioxide （COa） concentration under CFG and YY conditions at Luancheng Agro-ecosystem Experimental Stations in the NCR The results from the CERES and APSIM wheat crop models were largely consistent and suggested that changes in climate variables influenced wheat grain yield in the NCR There was also significant variation in the sensitivity of winter wheat yield to climate variables under different water （CFG and YY） conditions. While a temperature increase of 2℃ was the threshold beyond which temperature negatively influenced wheat yield under CFG, a temperature rise exceeding 1℃ decreased winter wheat grain yield under YY. A decrease in solar radiation decreased wheat grain yield under both CFG and YY conditions. Although the sensitivity of winter wheat yield to precipitation was small under the CFG, yield decreased significantly with decreasing precipitation under the rain- fed YY treatment. The results also suggest that wheat yield under CFG linearly increased by ≈ 3.5% per 60 ppm （parts per million） increase in CO2 concentration from 380 to560ppm, and yield under YY increased linearly by ≈ 7.0% for the same increase in CO2 concentration.

Regional Soil Mapping Using Multi-Grade Representative Sampling and a Fuzzy Membership-Based Mapping Approach

High-resolution and detailed regional soil spatial distribution information is increasingly needed for ecological modeling and land resource management. For areas with no point data, regional soil mapping includes two steps： soil sampling and soil mapping. Because sampling over a large area is costly, efficient sampling strategies are required. A multi-grade representative sampling strategy, which designs a small number of representative samples with different representative grades to depict soil spatial variations at different scales, could be a potentially efficient sampling strategy for regional soil mapping. Additionally, a suitable soil mapping approach is needed to map regional soil variations based on a small number of samples. In this study, the multi-grade representative sampling strategy was applied and a fuzzy membership-weighted soil mapping approach was developed to map soil sand percentage and soil organic carbon （SOC） at 0-20 and 20-40 cm depths in a study area of 5 900 km2 in Anhui Province of China. First, geographical sub-areas were delineated using a parent lithology data layer. Next, fuzzy c-means clustering was applied to two climate and four terrain variables in each stratum. The clustering results （environmental cluster chains） were used to locate representative samples. Evaluations based on an independent validation sample set showed that the addition of samples with lower representativeness generally led to a decrease of root mean square error （RMSE）. The declining rates of RMSE with the addition of samples slowed down for 20-40 cm depth, but fluctuated for 0-20 cm depth. The predicted SOC maps based on the representative samples exhibited higher accuracy, especially for soil depth 20-40 cm, as compared to those based on legacy soil data. Multi-grade representative sampling could be an effective sampling strategy at a regional scale. This sampling strategy, combined with the fuzzy membership-based mapping approach, could be an optional effective framework for regional soil property mapping. A more detailed and accurate soft parent material map and the addition of environmental variables representing human activities would improve mapping accuracy.